The invention relates generally to materials for isolating or treating a surface, and more particularly to a flowable material for forming a barrier layer having low permeability over a contaminated underwater surface or a land surface.
A significant number of lakes, ponds, marshes, river beds and ocean areas near coastlines are contaminated with environmentally hazardous materials. Examples of such materials include polychlorinated biphenyls ("PCB's"), white phosphorus, synthetic organic compounds, and various metals. Many of these materials, once introduced by one means or another, settle on the bottoms of such bodies of water or become attached to sediments. The resulting contaminated sediments are detrimental to the ecosystem, especially wildlife which utilizes the body of water, such as fish, foraging waterfowl and small vertebrates. In some cases the contaminants are slowly released from the sediments and re-introduced into the water column.
In some cases, it is not feasible to remove or treat such sediment in situ. Thus, to prevent the wildlife from coming into contact with the contaminated sediment and to seal the sediment from coming into contact with the water column, it has been proposed to form an underwater barrier layer over the contaminated sediment. Previous methods have been relatively difficult and expensive to install, and have been susceptible to damage. Thus, it would be desirable to provide a durable, relatively simple and inexpensive material for forming a barrier layer over a contaminated underwater surface. At times it would also be desirable to provide a method of forming a barrier layer over a contaminated underwater surface which could be repeated occasionally to allow for replenishment of the barrier layer. Other times it would be advantageous to form a more permanent underwater barrier layer which forms a hard shell over the contaminated surface. It would frequently be desirable to apply a material to the underwater surface to treat a particular type of contamination, or to restore or improve the surface.
Landfill sites are typically constructed by completing an excavation in the ground and lining the excavation to form a containing system prior to filling with waste materials. Unfortunately, the landfill is susceptible to leaching contaminants into the surrounding ground and possibly into the water table. The upper surface of the landfill attracts pests such as birds and rodents which can possibly carry diseases. Accordingly, it would be desirable to provide a low permeability barrier layer useful as a liner for a landfill to prevent the leaching of contaminants into the ground, and useful as a low permeability cap to keep pests away from the waste material and to minimize infiltration of water. If the landfill were covered by such a cap or included such a liner system, it would be important for quality control purposes to provide a relatively uniform distribution of materials in the cap or liner system.
In addition to landfill sites, other land surfaces such as newly excavated ponds or reservoirs could also benefit from such a barrier layer to hold the water in and prevent leakage into the surrounding area. A barrier layer could also be used to cover hazardous waste sites. Thus, there is a need for a material capable of forming a low permeability barrier layer on land surfaces. It would particularly be advantageous if the barrier layer could withstand repeated freeze/thaw and dehydration/rehydration cycles resulting from meteorological or climatological variances. In remediation projects it could be advantageous to use free-flowing aggregate-like materials to fill excavations where stability and a water retarding barrier are desirable.